That is good to know. I got the same thought from the manual. However, can there be a tool that will depress the valve and allow the removal of the shim(s)? The one and only Rocket that I did the valve inspection did not need any changes.
Not sure if there is enough room to attempt using any kind of tool. I'm about to find out. With little over 9,000 on the clock, i'll be due for a lookee!